Eye and Blood Proteins Show Strong Links to Cognitive Performance

Recent research has identified significant connections between specific proteins present in the eye and blood and cognitive function scores. The study, conducted by scientists at Boston University School of Medicine and Boston Medical Center, focused on the protein Slit Guidance Ligand 2 (SLIT2) and its levels in bodily fluids. Prior research suggested a link between SLIT2 levels and late-onset dementia, including Alzheimer's disease, but these findings lacked validation through reliable assays. This new investigation measured SLIT2 concentrations in the vitreous humor, the gel-like substance in the eye, and blood plasma of middle-aged individuals undergoing eye surgery.

The study involved 79 participants with an average age of 56 years, who underwent neurocognitive assessment, including the Montreal Cognitive Assessment (MoCA) and verbal memory tests. Using a highly sensitive immunoassay, researchers analyzed SLIT2 levels and found that lower SLIT2 concentrations in the vitreous humor correlated with poorer cognitive scores. Conversely, higher levels in plasma were also associated with reduced cognitive performance. Interestingly, SLIT2 levels in the eye's vitreous humor were up to seven times higher than in plasma, but the levels in these two fluids did not show a direct correlation.

The findings remained significant after accounting for factors such as age, sex, race, diabetic status, and other health conditions like diabetic retinopathy and glaucoma. The study suggests that ocular fluids could serve as valuable sources for early detection of neurodegenerative diseases. "Our results indicate that SLIT2, highly expressed in the retina, is linked to cognitive health, highlighting the potential of eye-based biomarkers for neurodegeneration," states co-author Dr. Manju L. Subramanian.

This groundbreaking research underscores the importance of the eye as a window to brain health and opens new avenues for early diagnosis and intervention. The study's results are published in the Journal of Alzheimer's Disease and were presented at the 2025 ARVO Annual Meeting in Salt Lake City, Utah.